Assessment of Landslides Occurred in Himachal Pradesh Over Last Two Decades

Assessment of landslides occurred in Himachal Pradesh over last two decades

Vidya Sagar Khanduri1 Sachin Verma2 1Assistant Professor, School of Civil Engineering, Lovely Professional University, Phagwara, 2M. Tech scholar, School of Civil Engineering, Lovely Professional University, Phagwara.

Abstract

Himachal Pradesh is hill state of India and widely affected by natural disasters. This is mainly vulnerable to earthquake and landslide. Landslide occurs when soil slides downward and outward respect to remaining mass. This review article has shown current study of causal factor done for landslide occurrence in the area. It is found that the change in climatic conditions such as increase in precipitation over years, geological, hydro-geological variables, earthquakes and anthropogenic interference has increased the landslide susceptibility of area. Use of landslide susceptibility zonation provides good idea for land use pattern. Several feasible solutions are also discussed.

Keywords: Land slide, earthquake, geotechnical investigation, landslide susceptibility zonation, precipitation.

1. Introduction Landslide is common word used to describe various type of slope movement. Vrane in 1978 has classified landslide as flow, falls, spreads, translational slides, topples and rotational slide. Himachal Pradesh is hill state of India and famous tourist attraction center [1]. According to disaster policy of Himachal landslide is one of main hazard in the state. Mountains of Himalayas are geologically seen as very young mountains. In these young and not so stable slope events of landslide are increasing due to activities of human like cutting of road, deforestation and changes in agriculture crops requiring more intense watering [2]. Research done by Surya Prakash has clearly shown that west and North West area of Himalayas suffer more landslide compare to northeast and south India. In his data collection from 1800 to 2011 he had found that total of 3971 people loss there life out of which 1946 were from west and north west region of Himalayas [3] .Global pattern of loss of life from landslide found that maximum number of loss in term of life due to landslide is found to be occurring along Himalayan arc and china [4]. Objective of present study is to understand causal factors effecting landslide in the state and provide feasible solutions for landslide as there is need of more scientific and engineered study of landslide problem at Himachal Pradesh.

2. Factor effecting landslide Popescu in his work has shown importance of understanding caustic factor for finding best cost-effective solution for landslide problem. There is list of causal factors made by IUGS WG/L Commission on Causes of Landslides in well- arranged order. There is two type of casual factor affecting the landslide: preparatory causal factor, triggering causal factor. As name signify preparatory casual factor responsible for making slope vulnerable to landslide whereas triggering factor initiate the movement. [5] Most of time there are several causal factors responsible for landslide such as ground condition, geomorphic process, physical process, manmade process. In most of landslide triggering factor is precipitation. Water cause increase in pore water pressure in soil which decrease shear resistance

Table 1 brief list of casual factor responsible for landslide. Natural causes Human causes Prolonged rainfall Deforestation Earthquake Construction Soil composition Animal grazing

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2.1 Rainfall behavior in the area Number of case study in area has shown that rainfall was triggering factor for landslide in Himachal Pradesh. it was observed that normal annual rainfall of Himachal Pradesh was 1267 ± 375 mm during period of 1971-2014. Average 66 rainy days observed through year. It was observed that rainfall more than 1000 mm which having probability of occurring more than 75% was at sixteen out of forty stations (Dehra, Dharamshala, Malan, Kangra, Nurpur, Palampu, Paonta, Nahan, Dhaulakuan Jogindernagar and Sarkaghat) [7]. Study of 1951 to 2005 observed that maximum value of mean annual rainfall is located at Dharmashala region with intensity of 2923.4 mm and lowest mean annual rainfall is at Sangla having intensity of 752.3mm is found increase in pattern of heavy rainfall event in Palampur region. It is observed that rainfall intensity is increasing in region where as number of rainy days is decreasing. maximum contribution of precipitation in state is by monsoon rain(78.55%) , whereas pre-monsoon contribute (9.17%), winter rains which generally occur due to western disturbance is 8.06% and post monsoon is (4.21%) [8] Western Disturbance is rainfall observed in northwest part of India during winter it is originating in the Mediterranean Sea and the Atlantic Ocean. Winter precipitation is found to be more at higher altitudes as compared to lower altitudes. During his research done in 2015 low precipitation is recorded in November and December month lead to bad effect to winter crop and more air pollution in city [9]. Decreasing trend is seen in frequency of WDs over Himachal Pradesh in his research of time period 1997-2007 [10]. Five-year data (2014-2018) of rainfall of every month has been collected from metrological department, it has been found that Kangra have maximum rainfall intensity of 924 mm in august 2018.it is also found that overall rainfall of state has shown increasing trend in year 2018 [11].

Fig.2 Kangra, H.P rainfall data from 2014 to 2018

Fig.3 rainfall data of Lahul and spiti 2014-2018

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Fig.4 showing monsoon rainfall intensity graph from 2017 to 2018

2.2 Earthquake When there is displacement of two block of rock along fault then earthquake happen. .Level of magnitude and distance from epicenter give level of shaking at susceptible slope Material which is most vulnerable to earthquake induced landslide is weakly cemented rocks, granular man-made fill, residual and colluvial sand, granular deltaic deposits loess, high-indurated rocks with pervasive or prominent discontinuities, cemented soils, volcanic soils containing sensitive clay, granular alluvium[12]. According to earthquake hazard profile of state the tectonic features in the Himachal Pradesh include the Main Central Thrust and main boundary fault which are parallel to the strike length of Himalayas. The Jutogh Giri, Krol, and Nahan thrusts also present in state. There is also presence of small faults, like Kaurik Fault due to which1975 Kinnaur earthquake happened. Kangra and Dharamshala has suffered biggest landslide of state in year 1905, having magnitude 8.0 in Richter scale. It has cause death of 20000 persons. more than 250 earthquake has been seen having magnitude more than 4.0 in 90 years. 1906 kullu earthquake M 6.4 Kullu and 1975 Lahual-Kinnaur Spiti earthquake M 6.8 was also major earthquake in area. Kullu, Kangra, Hamirpur, Bilaspur, Una, Mandi, and Chamba, Districts lie in zone five. districts of Kinnaur Lahual and Spiti, , Solan Shimla, and Sirmaur lie in zone four[2] Roger used geodetic, historical and seismological data to identify segment of Himalayas that remain enraptured. It is found that out of fifteen segments ten segment of the Main Himalayan Thrust arc are found to sufficiently mature to generate earthquake of more than 8 Mw. Estimated death is more than 100000 due to increase in population and poor quality construction. [13] Table.2 list of earthquake occur in past. Earthquake Location Magnitude

4-April-1905 Kangra 320 18’00” 8 760 15’00” 28-Feb-1906 -Kullu 320 00’00” 7 770 00’00” 5-Feb-1930 Shila Kiepr 310 42’00” 5.5 770 00’00”

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22-June-1945 -Minu ,Chmaba 320 36’00” 6.5 750 54’00” 10-July-1947 – Minu,Chmaba 320 36’00” 6.2 750 54’00” 12-August1950 Minu,Chmaba 320 36’00” 6.0 750 54’00”

19-Jan-1975 Distt.Kinnaur 310 56’24” 5.5 780 31’48” 26-April-1986 Near Nag Dal 320 19’00” 5.5 760 24’00” 11-Nov-2004 Bharmour, 32.442 N, 5.1 76.512 E,

3. Possible remedy Mitigation prevention and Preparedness are the techniques used by stated disaster management authority to avoid any hazard convert into disaster. in case of landslide hazard Role of vulnerability mapping is highly recommended to be used in mitigation process which is done by producing landslide vulnerability zonation map with help GIS software’s. Whereas use of remedial measure, improving existing infrastructure or replace old one is recommended in point of view of prevention. While in preparedness process use of early warning system, use of information technology, medical preparedness and training and mock drill is highly advised. [2] 3.1 Landslide susceptibility zonation for prevention Landslide susceptibility is spatial prediction of landslide. To find place of landslide happening with help of various causal factors. There are different approaches for LSZ. But mainly these are classified as qualitative and quantitative approach which can be subdivided as distribution analysis Geomorphic Analysis Map Combination Approach Quantitative Approaches, Statistical Analysis, Probabilistic Approach, Distribution-Free Approaches [14]. Table.3 list of LSZ work in HP. LSZ area Method Author 1 Dharmashala Information value Swatisharma, abhirishkumar 2 Nahan to Rajgarh Machine learning Vijendra Kumar Pandey, 3 national highway154A information value and Kanwarpreet Singh Virender frequency ratio Kumar 4 between Giri and Tons Rivers GIS based technique Piyoosh Rautelal 5 Kullu district Information value Laxmi Devi Versain, 6 Kullu district Various Laxmi Devi Versain

In study conducted by Swati Sharma and AK mahajan they performed landslide susceptibility zonation in dharmashala region of distt kangda in Himachal Pradesh India. landslides were discovered and confirmed by Google Earth images. Various causative factor is selected road buffer litho logy, slope, aspect, soil type density,

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© 2018 JETIR November 2018, Volume 5, Issue 11 www.jetir.org (ISSN-2349-5162) major fault density, drainage land cover. Computation of total landslide pixels for every subclass as well as landslide pixel is done to find information value. Information value of every subclass is then used to attach layer using ArcGIS software and landslide susceptibility map was made as shown. Out of total landslides 0.66 sq. km, 0.65 sq. km landslide fall in very high susceptibility class. [15]

Fig.5 Landslide susceptibility zonation map of Dharamshala.

Also, in another study conducted by Panday, Vijandra developed landslide zonation map from Nahan to Rajagarh the point of this examination is to research the reasons for avalanches in the Himalayan area and investigation of their sedimentary qualities. It is found that landslide frequently occur in lesser Himalayan rang. Here in this study author find characteristics of the sediments and find best susceptibility zonation map by comparing results from different approach.[16]

3.2 Feasible solution for mitigation pocescu has provided list of mitigation option which can be implemented in site, which include method like accepting it, avoiding it, decreasing its consequences, early warning system and monitoring landslide. Landslide can be prevented either by decreasing the driving force or increase in resisting force. Solution available can be broadly classified into 4 groups as; change in slope geometry, drainage, retaining structure, internal slope reinforcement [17]. Drainage is most important method in contrast to landslide remedy as presence of water in soil makes soil strength to lose its shear strength and increase its pore water pressure and slope to reduce its resisting force. Drain serves its function in reduction of pore water pressure [18]. In deep-seated landslide it is recommended to change its slope geometry. Also, it is observed that remedial measure is mostly used in combination. Debris flow which is very destructive can be mitigated by applying check dams. While different method of remediation is available it must be selected after looking at all aspect like engineering aspect, legal aspect, social aspect, environmental aspect. Ramli try to improve wall resistance against lateral movement with help of new interlocking systems in gabion wall. He suggested use of hexagonal shape block instead of regular rectangular shape as they found to be more stable in application of load experiment also show that less structural inertia is experienced by it which is 7.6% in first loading stage and 10.8% in last three loading stage. It is observed that gabion wall has more advantage as compare to retaining wall by acting many ways 1) to provide reinforcement which can handle many stresses like tension stress shear stress 2) they provide much batter load distribution as they not act to resist all forces and show some deformation. JETIRDR06004 Journal of Emerging Technologies and Innovative Research (JETIR) www.jetir.org 27

3) They provide much batter drainage as they allow water to pass through it while resisting backfill [19]. Huang have discussed and provided remedy for completely destroyed slope which was present in Tiwan. Use of soil cement was prescribed in solution. Has used MCDA (multi-criteria decision analysis) approach method to find best remedial measure landslide occur at Hsinchu city in Tiwan. Site investigation was done to know geological geographical and soy information of site testing was done to obtain all geotechnical properties of soil and then assessment of failure of slope is by preparing numerical model [20]. Use of numerical molding is seen on various case studies in Himachal Pradesh to find FOS or analyze stress distribution and deformation pattern during time of failure as observed in kotropi remedial measure [21]

Table 4 A brief list of landslide remedial measures Modification of Retaining Internal slope reinforcement slope geometry Drainage structures

Removing or Surface drains Gravity Rock bolts Adding Drainage tunnels, retaining walls Micro piles material Vacuum Crib block walls Soil nailing Reducing slope angle dewatering Gabion Anchors Grouting stone columns Heat Electroosmotic walls treatment Vegetation planting

4. Conclusion Heavy Rainfall is found to be main trigging factor for most of landslide in Himachal Pradesh. Researches has shown high rainfall at Dehra, Dharamshala, Malan, Kangra, Nurpur, Palampu, Paonta, Nahan, Dhaulakuan Jogindernagar, sarkaghat area. While decrease in precipitation due to western disturbance is observed. There is presence of main boundary fault (MBF) and Main Central Thrust (MCT), Krol, the Giri, Jutogh and Nahan thrusts small faults, like Kaurik Fault which make area highly susceptible to earthquake and earthquake induced landslides. Research has shown high probably of earthquake more than 8 Mw in future of slope which makes it important to ensure safety in term of earthquake induced landslide. Landslide susceptibility zonation is found to be very important tool for landslide mitigation. There is need for preparation of more landslide susceptibility map focusing on restricted area. As widening of road network is going in large scale there is need of more research for understanding impact of anthropogenic and physical factor on landslides in area. Mostly retaining wall is used for stabilizing slopes in this area there is need of adoption different method as it can cause failure during construction. Reference 1. Varnes, D. J. (1978). Slope movement types and processes. Special report, 176, 11- 33. 2. https://hpsdma.nic.in/ 3. Parkash, S. (2011). Historical records of socio-economically significant landslides in India. J South Asia Disaster Studies, 4(2), 177-204. 4. Petley, D. (2012). Global patterns of loss of life from landslides. Geology, 40(10), 927930.

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5. Popescu, M. E., & Sasahara, K. (2009). Engineering measures for landslide disaster mitigation. In Landslides–Disaster Risk Reduction (pp. 609-631). Springer, Berlin, Heidelberg 6. Schuster, R. L., & Wieczorek, G. F. (2002, June). Landslide triggers and types. In Proceedings of the 1st European conference on landslides, Prague. Balkema, Rotterdam (pp. 59-78). 7. Singh, P., Kumar, V., Thomas, T., & Arora, M. (2008). Changes in rainfall and relative humidity in river basins in northwest and central India. Hydrological Processes: An International Journal, 22(16), 2982- 2992 8. Jaswal, A. K., Bhan, S. C., Karandikar, A. S., & Gujar, M. K. (2015). Seasonal and annual rainfall trends in Himachal Pradesh during 1951-2005. Mausam, 66(2), 247-264. 9. Basu, S., Bieniek, P. A., & Deoras, A. (2017). An investigation of reduced western disturbance activity over Northwest India in NovemberDecember 2015 compared to 2014-A case study. Asia-Pacific Journal of Atmospheric Sciences, 53(1), 75-83. 10. Kumar, N., Yadav, B. P., Gahlot, S., & Singh, M. (2015). Winter frequency of western disturbances and precipitation indices over 11. Himachal Pradesh, India: 19772007. Atmósfera, 28(1), 63-70. 12. http://www.weathershimla.nic.in/ 13. Verma, M., & Bansal, B. K. (2013). Active fault mapping: An initiative towards seismic hazard assessment in India. Journal of the Geological Society of India, 82(2), 103-106. 14. Himachal Pradesh, India: 19772007. Atmósfera, 28(1), 63-70. potential. Geological Society, London, Special Publications, 483, SP483-16. 15. Dietrich, W. D., Lin, B., Globus, M. Y. T., Green, E. J., Ginsberg, M. D., & Busto, R. (1995). Effect of delayed MK-801 (dizocilpine) treatment with or without immediate postischemic hypothermia on chronic neuronal survival after global forebrain ischemia in rats. Journal of Cerebral Blood Flow & Metabolism, 15(6), 960-968. 16. Popescu, M. E. (2002, July). Landslide causal factors and landslide remediatial options. In 3rd 17. International Conference on Landslides, Slope Stability and Safety of Infra-Structures(pp. 61-81). 18. Zhu, J. H., & Anderson, S. A. (1998). Determination of shear strength of Hawaiian residual soil subjected to rainfall-induced landslides. Géotechnique, 48(1), 73-82. 19. Ramli, M., Karasu, T., & Dawood, E. T. (2013). The stability of gabion walls for earth retaining structures. Alexandria Engineering Journal, 52(4), 705-710. 20. Wu, J. Y., Huang, K., & Sungkar, M. (2017). Remediation of slope failure by compacted soil-cement fill. Journal of Performance of Constructed Facilities, 31(4), 04017022. 21. Sharma, P., Rawat, S., & Gupta, A. K. Study and Remedy of Kotropi Landslide in Himachal Pradesh, India. Indian Geotechnical Journal, 1-17.

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APPENDIX

List of landslides in past Table1. brief list of pasts occurred landslide in Himachal Pradesh Sn. Name Reason Date Remarks

1 Chirgaon Cloudburst 11/81997 kumar2007

2 Sutlej Valley Cloudburst 30/72000 kumar2007

3 Kullu Flash flood 16/7/2003 Mazari and Sah 2004

4 Shimla Heavy rainfall 15/8/ 2007 100 killed

5 Chittkul Heavy rainfall 15/82007 65 killed

6 Nehrukund Unknown 18/3/ 2008 25 Killed

7 Shimla Continous rainfall 21/9/2008 42 killed, 13 houses collapsed

8 Kotropi mandi Continous rainfall 13/8/2017 47 killed,

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